Medieval Total War is not installing!

I have all the systems requirements, the game has worked on my p.c before.
the disc is fine, I even had it cleaned.
It loads up to 99% when installing (even accepts both discs that are needed for installation process) then a message comes up saying:

setup has detected errors in installation process


I also had a problem which said:

Please close unInstallShield and restart setup
Error 432.

I have no idea what I did but it went away and the game started installing but it still gets to 99% then a minute later when its meant to be fully installed a message comes up saying theres errors.

How do I find out what these errors are and more importantly how do I resolve the problem so I can play the game?

Please help, I would be ever so grateful!

Well i think that you have must have install any kind of firewall on your system and that is the reason why it is not taking the game on to the system. so now what i want you to do here is that just make sure whether you have any such firewall installed or not and if it is then disable it until the whole installation starts and complete. I hope that you are getting my point here and also will be able to solve the issues without and problem.